PDB analysing

Iam working with PDB files, and have some problems with extracting and calculating...

a PDB file look like thise for those how dont know:
see attached file

What I want is to read the whole file, find were there are lines with CA
atoms and calculate the distance between every two CA atom in a xzy-plane
and if the distance is over 4.3 it should give me the position of the two
CA atoms.

An exampel will be:
look first were there are a CA atom
in a line in the PDB file. it can look like that :

ATOM 345 CA LYS A 24 129.78 32.123 23.98

then I want to find another line with CA atom in the file, it could be:

ATOM 746 CA ARG A 43.98 543.98 65.98

(I have done that by regular expression, but still have some problems )

the last 3 numbers are the xyz coordinate for the CA atoms. What I want now is to calculate the distance between the to given atoms by using eq. for distance between two points in a 3 D:
sqrt(($ax - $bx) ** 2 + ($ay - $by) ** 2+ ($az - $bz) ** 2)
if the distance is over 4.3 the program should give me a massege at witch atom possition the distance is over 4.3...

hope you understand

what I have done untill now :
CA atom is what I am looking for is is my alpha carbon

(2 is the no of the atom CA indicate that its a carbon alpha atom and the 3 dicimale numbers indicate the x-coordinate, y-coordinate and z- cordinate)

I wanna now calculate the distance between every two alpha carbon in the given data set, meaning that calculate the distance between 2 CA and 10 CA and then between 10 CA AND 28 CA and so on....
using the distance between two point in a 3 D I cant calculate the distance. Now if the distance is over 4.3 it should give me a message at which atoms no. it is.

Hi. so this is actually a continuation from another question of mine[Here](https://www.daniweb.com/programming/software-development/threads/506795/dynamically-add-values-into-datagridview-cell-from-listbox-vb2010) but i was advised to start a new thread as the original question …

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